RETIRED
15th March 2009, 04:47 PM
After a number of requests from woodturning club and forum members to write about my thoughts on woodturning and allied subjects I have finally started.
Hopefully it will help beginners in particular select tools and machinery and not make the same mistakes that most have, me included.
Please remember that these opinions are mine and like most people I have slight bias towards some things but I will try to keep that bias out of this as much as I can.
I will break it up into sections and post up each bit when I can.
The lathe and its bits.99255
First off: The Lathe. I am talking about the most common lathes that most will buy or use.
Technically it is a machine that spins wood around so that we can apply a bit of steel to the timber to put shapes into it.
There is a plethora of lathes on the market at the moment to suit all budgets and levels of competence but getting a good one with the right features for you is not hard.
I have found that a lot of people have trouble turning not so much because of their own lack of skill but the machine is not capable of doing what they want.
We will start with construction first and move through the components.
It really does not matter if it is constructed of wood, steel or cast iron as long as some simple criteria are met. I have seen and owned good and bad in all of them.
The bed of the lathe is probably the single most important part of the lathe. It must be straight, strong and stable because everything else hangs off it in most cases.
You may notice that I did not mention flat because I have seen some beds that have a raised "V" like metal turning lathes to locate the tail stock. They generally have a saddle like metal turning lathes as well. These are rare. In all other cases the ways should be flat.
It should have some webbing or strengthening at the lower portions to stop spread of the ways and resist torsional twisting.9925499257
Pressed steel (flimsy) components for the bed should be avoided as should hollow steel bars.
Single bars (Myford, not the Chinese clones) and double solid steel bars like the Record or older Teknatool are very strong but care is needed in fitting them to a stand to make sure you keep them co planar.
When bolting all lathes down you should be cautious that you are not bending them.
Long beds should have some anchor points midway for support. 99256
Wooden beds benefit from having angle or flat iron fitted to the top to stop wear from the banjo or tailstock when being moved.
Arguments rage as to whether or not cast iron is better than steel. To be honest I have not noticed much difference provided that the above is adhered to and good sized steel section is used.
The biggest thing going for cast iron is weight (more on that later) and ease of manufacture. It is far easier to cast all the components than fabricate them with the problems of pulling when welding.
The headstock.
The headstock consists of a casing that contains a shaft that rotates in bearings. It generally has pulleys at one end or in the centre.
It can be again wood, cast iron or steel.99252
The headstock takes the brunt of all the work. It has every force known applied to it to wrench it from its mountings.
Lets look at the forces applied. In spindle turning it has longitudinal force applied by the tailstock which tries to push it over. It also has a twisting force if the wood is out of balance. This also acts on the mounting point. Out of balance timber is also trying to rip it upwards or shove it downwards through the bed. 99253
Not a happy chappy our headstock.
The headstock therefore must be well fixed to the bed with a good bearing surface and strong enough to resist all that.
A swivel headstock is a matter of personal preference and depends on the work you do. I personally love mine on the Teknatool for doing small bowls and goblets as you don't have to lean across the bed for hollowing.
Not a neccessity but nice to have.
If you do get a swivel headstock make sure that it has positive detents and locks down flat on the mounting.
The same forces also apply to the shaft holding our timber.
Most shafts these days are 30mm or more in Diameter. This is strong enough for nearly all applications of the work that can be turned on size of the lathe. Bigger work needs a bigger shaft. Our big lathe has a 50mm solid steel shaft because of the weight and forces exerted on it.
It is preferable that the shaft be drilled right through with a No.2 Morse taper at the drive end. Most accessories that use a morse taper use this size.
Being drilled right through enables a knock out bar to be used to eject the drive. It also allows the use of draw bolts to lock some drives in.
The industry for a long time used about 6 different threads on the nose of the spindle which made fitting face plates or chucks to different lathes a nightmare.
Fortunately they seem to have settled on one at least in Australia, this being 30mm x 3.5mm.
The bearings that support the shaft also have an additional problem in that they have to rotate whilst coping with the other forces. Spacing of the bearings is important. They should be no closer than 150mm apart (not talking about mini lathes) to support the shaft. If too close the shaft can "wobble" using the bearings as a fulcrum. If too far apart the shaft can bend in the middle.
Some manufacturers use three bearings.
The bearings should have the ability to take axial as well as radial load. Whether they are tapered roller or ball bearings does not matter in my opinion as I have seen failures in both types.
The tapered roller bearings generally have a means of adjusting the free play and this can bring them unstuck if not adjusted correctly.
Most bearings these days are sealed so are lubricated for life.
A little tip for those in colder climates is to run the lathe for a few minutes with no load before you start work to warm the grease up to distribute it around the bearing. It doesn't hurt in warmer climates too.
Also fitted to the shaft is generally an indexing head of 12, 24 or 48 holes. It is handy if doing clocks to space the numbers but its main use is to lock the spindle at various degrees so that you can reed or flute a spindle. The same applies to applying decoration to a bowl or other face plate work.
It is also used as a spindle lock in most cases but be careful that you don't "strip" it. If it is not to be used as that most manufacturers warn you of it and have other means to lock the spindle for removing chucks etc.
Not a necessity as one can be added later.
The last thing that the shaft does is support the pulleys to allow you to change speeds.
In this day and age most pulleys are multivee. The advantages of these belts is they transfer power better without as much slippage and run quieter than the older "V" belts.
If a multivee is noisy a drop of brake fluid will generally quieten it.
I prefer my pulleys on the outside of the shaft so that if a belt breaks it is easily replaced.
Pulleys mounted between the bearings require the shaft to be taken out to replace the belt. If faced with this situation, replace the bearings as well.
Another tip: put another spare belt in the housing and tape it out of the way.
It is a rare occurence that belts break these days. If it does, investigate why and fix the problem before fitting a new one.
Pulleys should be easily accessible for changing speeds. More on that later.
To be continued.
Hopefully it will help beginners in particular select tools and machinery and not make the same mistakes that most have, me included.
Please remember that these opinions are mine and like most people I have slight bias towards some things but I will try to keep that bias out of this as much as I can.
I will break it up into sections and post up each bit when I can.
The lathe and its bits.99255
First off: The Lathe. I am talking about the most common lathes that most will buy or use.
Technically it is a machine that spins wood around so that we can apply a bit of steel to the timber to put shapes into it.
There is a plethora of lathes on the market at the moment to suit all budgets and levels of competence but getting a good one with the right features for you is not hard.
I have found that a lot of people have trouble turning not so much because of their own lack of skill but the machine is not capable of doing what they want.
We will start with construction first and move through the components.
It really does not matter if it is constructed of wood, steel or cast iron as long as some simple criteria are met. I have seen and owned good and bad in all of them.
The bed of the lathe is probably the single most important part of the lathe. It must be straight, strong and stable because everything else hangs off it in most cases.
You may notice that I did not mention flat because I have seen some beds that have a raised "V" like metal turning lathes to locate the tail stock. They generally have a saddle like metal turning lathes as well. These are rare. In all other cases the ways should be flat.
It should have some webbing or strengthening at the lower portions to stop spread of the ways and resist torsional twisting.9925499257
Pressed steel (flimsy) components for the bed should be avoided as should hollow steel bars.
Single bars (Myford, not the Chinese clones) and double solid steel bars like the Record or older Teknatool are very strong but care is needed in fitting them to a stand to make sure you keep them co planar.
When bolting all lathes down you should be cautious that you are not bending them.
Long beds should have some anchor points midway for support. 99256
Wooden beds benefit from having angle or flat iron fitted to the top to stop wear from the banjo or tailstock when being moved.
Arguments rage as to whether or not cast iron is better than steel. To be honest I have not noticed much difference provided that the above is adhered to and good sized steel section is used.
The biggest thing going for cast iron is weight (more on that later) and ease of manufacture. It is far easier to cast all the components than fabricate them with the problems of pulling when welding.
The headstock.
The headstock consists of a casing that contains a shaft that rotates in bearings. It generally has pulleys at one end or in the centre.
It can be again wood, cast iron or steel.99252
The headstock takes the brunt of all the work. It has every force known applied to it to wrench it from its mountings.
Lets look at the forces applied. In spindle turning it has longitudinal force applied by the tailstock which tries to push it over. It also has a twisting force if the wood is out of balance. This also acts on the mounting point. Out of balance timber is also trying to rip it upwards or shove it downwards through the bed. 99253
Not a happy chappy our headstock.
The headstock therefore must be well fixed to the bed with a good bearing surface and strong enough to resist all that.
A swivel headstock is a matter of personal preference and depends on the work you do. I personally love mine on the Teknatool for doing small bowls and goblets as you don't have to lean across the bed for hollowing.
Not a neccessity but nice to have.
If you do get a swivel headstock make sure that it has positive detents and locks down flat on the mounting.
The same forces also apply to the shaft holding our timber.
Most shafts these days are 30mm or more in Diameter. This is strong enough for nearly all applications of the work that can be turned on size of the lathe. Bigger work needs a bigger shaft. Our big lathe has a 50mm solid steel shaft because of the weight and forces exerted on it.
It is preferable that the shaft be drilled right through with a No.2 Morse taper at the drive end. Most accessories that use a morse taper use this size.
Being drilled right through enables a knock out bar to be used to eject the drive. It also allows the use of draw bolts to lock some drives in.
The industry for a long time used about 6 different threads on the nose of the spindle which made fitting face plates or chucks to different lathes a nightmare.
Fortunately they seem to have settled on one at least in Australia, this being 30mm x 3.5mm.
The bearings that support the shaft also have an additional problem in that they have to rotate whilst coping with the other forces. Spacing of the bearings is important. They should be no closer than 150mm apart (not talking about mini lathes) to support the shaft. If too close the shaft can "wobble" using the bearings as a fulcrum. If too far apart the shaft can bend in the middle.
Some manufacturers use three bearings.
The bearings should have the ability to take axial as well as radial load. Whether they are tapered roller or ball bearings does not matter in my opinion as I have seen failures in both types.
The tapered roller bearings generally have a means of adjusting the free play and this can bring them unstuck if not adjusted correctly.
Most bearings these days are sealed so are lubricated for life.
A little tip for those in colder climates is to run the lathe for a few minutes with no load before you start work to warm the grease up to distribute it around the bearing. It doesn't hurt in warmer climates too.
Also fitted to the shaft is generally an indexing head of 12, 24 or 48 holes. It is handy if doing clocks to space the numbers but its main use is to lock the spindle at various degrees so that you can reed or flute a spindle. The same applies to applying decoration to a bowl or other face plate work.
It is also used as a spindle lock in most cases but be careful that you don't "strip" it. If it is not to be used as that most manufacturers warn you of it and have other means to lock the spindle for removing chucks etc.
Not a necessity as one can be added later.
The last thing that the shaft does is support the pulleys to allow you to change speeds.
In this day and age most pulleys are multivee. The advantages of these belts is they transfer power better without as much slippage and run quieter than the older "V" belts.
If a multivee is noisy a drop of brake fluid will generally quieten it.
I prefer my pulleys on the outside of the shaft so that if a belt breaks it is easily replaced.
Pulleys mounted between the bearings require the shaft to be taken out to replace the belt. If faced with this situation, replace the bearings as well.
Another tip: put another spare belt in the housing and tape it out of the way.
It is a rare occurence that belts break these days. If it does, investigate why and fix the problem before fitting a new one.
Pulleys should be easily accessible for changing speeds. More on that later.
To be continued.